Liquid crystal display device

ABSTRACT

A liquid crystal display device and a fabrica tion method of such a liquid crystal display device which can reduce man-hours for fabrication are provided. The liquid crystal display device is characterized in that, on each pixel region at a liquid-crystal side of one of respective substrates which are arranged in an opposed manner while sandwiching a liquid crystal therebetween a thin film transistor which is driven by scanning signals from a gate signal line, a pixel electrode to which video signals from a drain signal line are supplied through the thin film transistor, and a capacity element which is formed between the pixel electrode and a holding capacity electrode, the capacity element is formed such that a semiconductor layer forming the same layer as a semiconductor layer of the thin film transistor, a first insulation film forming the same layer as a gate insulation film of the thin film transistor, the holding capacity electrode, a second insulation film and a metal layer are sequentially laminated from a substrate side, and the semiconductor layers and the metal layer are connected to each other, and the metal layer is formed as a reflector which occupies a portion of the pixel region.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a liquid crystal display device,and more particularly to a so-called partial-transmission type liquidcrystal display device.

[0003] 2. Description of the Related Art

[0004] A so-called partial-transmission type liquid crystal displaydevice is used as a small-sized liquid crystal display device for mobilephone and images on a display surface are recognized with the use of areflection light of sun beam or light of an incorporated backlight whennecessary.

[0005] That is, out of respective transparent substrates which arearranged in an opposed manner while sandwiching a liquid crystaltherebetween, on a liquid crystal surface side of one transparentsubstrate, pixel regions are defined by regions which are surrounded bygate signal lines extended in the y direction and arranged in parallelto the x direction and drain signal lines extended in the x directionand arranged in parallel to the y direction, and a thin film transistorwhich is driven with a supply of a scanning signal from one gate signalline and a pixel electrode to which a video signal is supplied from onedrain signal line through the thin film transistor are formed on therespective pixel region

[0006] This pixel electrode is, for example, made of a transparentelectrode such as ITO (Indium-Tin-Oxide). On the liquid crystal side ofthe other transparent substrate, an electric field is generated betweenthe pixel electrode and a counter electrode made of a transparentelectrode commonly formed on each pixel region, and the opticaltransmissivity of the liquid crystal in the pixel regions can becontrolled due to the electric field.

[0007] Then, with respect to these respective pixel regions, byproviding reflectors made of, for example, metal layers in approximatelyhalf of these regions, it becomes possible to give the liquid crystaldisplay device a function which enables a reflection-type display atportions where the reflectors are provided and a function which enablesa transmission-type display at portions where the reflectors are notprovided.

[0008] The constitution of this type of liquid crystal display device isdisclosed in detail in, for example, Japanese Patent Laid-open No.101992/1999 and Japanese Patent Laid-open No. 242226/1999.

[0009] However, the liquid crystal display device having such aconstitution has a complicated structure and requires a large number ofman-hours for fabrication and hence, it has been often pointed out thatthe cost is pushed up.

SUMMARY OF THE INVENTION

[0010] The present invention has been made in view of the abovecircumstance and it is an object of the present invention to provide aliquid crystal display device which can reduce the fabrication steps anda fabrication method thereof.

[0011] To simply explain a typical invention among inventions disclosedin the present application, it goes as follows.

[0012] That is, a liquid crystal display device according to the presentinvention is substantially characterized in that, on each pixel regionat a liquid-crystal side of one of respective substrates which arearranged in an opposed manner while sandwiching a liquid crystaltherebetween , a thin film transistor which is driven by a scanningsignal from a gate signal line, a pixel electrode to which a videosignal from a drain signal line is supplied through the thin filmtransistor, and a capacity element which is formed between the pixelelectrode and a holding capacity electrode are provided,

[0013] the capacity element is formed such that a semiconductor layerforming the same layer as a semiconductor layer of the thin filmtransistor, a first insulation film forming the same layer as a gateinsulation film of the thin film transistor, the holding capacityelectrode, a second insulation film and a metal layer are sequentiallylaminated from a substrate side, and the semiconductor layers and themetal layer are connected to each other, and

[0014] the metal layer is formed as a reflector which occupies a portionof the pixel region and, at the same time and is connected to the pixelelectrode which is formed above a third insulation film formed in thepixel region such that the third insulation film covers the metal layer.

[0015] In the liquid crystal display device having such a constitution,the reflector is configured as one electrode of the capacity element.

[0016] This means that the reflector is formed in forming one electrodeof the capacity element, so that the increase of the man-hours forfabrication can be suppressed or the man-hours can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a cross-sectional view showing one embodiment of a pixelof a liquid crystal display device according to the present invention.

[0018]FIG. 2 is a plan view showing one embodiment of a pixel of aliquid crystal display device according to the present invention and across-sectional view taken along a line 1-1 of FIG. 2 corresponds toFIG. 1.

[0019]FIG. 3 is an equivalent circuit diagram showing one embodiment ofa liquid crystal display device according to the present invention.

[0020]FIG. 4 is a step view showing one embodiment of a fabricationmethod of a liquid crystal display device according to the presentinvention, wherein FIG. 4 shows one fabrication step together with FIG.5 and FIG. 6.

[0021]FIG. 5 is a step view showing one embodiment of a fabricationmethod of a liquid crystal display device according to the presentinvention, wherein FIG. 5 shows one fabrication step together with FIG.4 and FIG. 6.

[0022]FIG. 6 is a step view showing one embodiment of a fabricationmethod of a liquid crystal display device according to the presentinvention, wherein FIG. 6 shows one fabrication step together with FIG.4 and FIG. 5.

[0023]FIG. 7 is a constitutional view showing another embodiment of aliquid crystal display device according to the present invention.

[0024]FIG. 8 is a constitutional view showing still another embodimentof a liquid crystal display device according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] An embodiment of a liquid crystal display device according to thepresent invention is explained hereinafter in conjunction with attacheddrawings.

[0026] <Overall Constitution>

[0027]FIG. 3 is an equivalent circuit diagram showing one embodiment ofa liquid crystal display device according to the present invention.Although the drawing is a circuit diagram, it is drawn corresponding toan actual geometrical arrangement.

[0028] In the drawing, a transparent substrate SUB1 is shown. Thistransparent substrate SUB1 is arranged such that the substrate SUB1faces another transparent substrate (not shown in the drawing) in anopposed manner while sandwiching a liquid crystal therebetween.

[0029] On a center portion except for a periphery of a liquid-crystalside surface of the transparent substrate SUB1, gate signal lines GLwhich are extended in the x direction and are arranged in parallel tothe y direction as well as drain signal lines DL which are extended inthe y direction and are arranged in parallel to the x direction areformed. Pixel regions are formed of regions which are surrounded bythese respective signal lines GL, DL.

[0030] A plurality of these pixel regions are arranged in a matrix arraythus constituting a display region 13.

[0031] Then, between the gate signal line GL and other neighboring gatesignal line GL, a holding capacity electrode wiring CL which is extendedin the x direction is formed and this holding capacity electrode wiringCL is made to form one capacity holding electrode CT of a capacityelement Cadd which will be explained later with respect to each pixelregion.

[0032] Each pixel element includes a thin film transistor TFT which isdriven by a supply of a scanning signal from one gate signal line GL anda transparent pixel electrode PIX to which a video signal from one drainsignal line DL is supplied through the thin film transistor TFT.Further, the holding capacity element Cadd is formed between the pixelelectrode PIX and the holding capacity electrode wiring CL.

[0033] Further, each gate signal line GL has both ends (left and rightsides in the drawing) thereof connected to a gate signal line drivecircuit 15 which is constituted of a semiconductor integrated circuitmounted on the transparent substrate SUB1 so as to enable the sequentialsupply of scanning signals outputted from the gate signal line drivecircuit 15 to respective gate signal lines GL.

[0034] Further, each drain signal line DL has one end (lower-side end inthe drawing) thereof connected to a drain signal line drive circuit 14which is constituted of a semiconductor integrated circuit mounted onthe transparent substrate SUB1 so as to enable the supply of videosignals matching the timing of the supply of the scanning signal torespective drain signal lines DL.

[0035] Still further, the holding capacity electrode wiring CL has oneend (left side in the drawing) thereof connected to a terminal Vcom.

[0036] This terminal Vcom is formed in parallel to input terminals 18,19, 100 formed on the periphery of the transparent substrate SUB1 and isheld at the same potential as a transparent counter electrode (not shownin the drawing) common to respective pixel regions on a liquid-crystalside surface of the other transparent substrate which is arranged in anopposed manner to the transparent substrate SUB1.

[0037] In the drawing, numeral 16 indicates a precharge circuit forcharging the drain signal lines DL, numeral 17 indicates a level shiftcircuit which makes digital signals (control signals) inputted to inputterminals 19, 100 have a voltage sufficient to drive the gate signalline drive circuit 15 and the drain signal line drive circuit 14.

[0038] <Constitution of Pixels>

[0039]FIG. 2 is a plan view showing one embodiment of the pixel regionof the liquid crystal display device according to the present inventionand a cross section taken along a line I-I is shown in FIG. 1.

[0040]FIG. 2 shows a constitution of one pixel region out of respectivepixel regions which constitutes the display region 13 shown in FIG. 3.Accordingly, respective pixel regions which are arranged in the left andright direction as well as in the up and down direction relative to thispixel region also have the same constitution.

[0041] In FIG. 1 and FIG. 2, first of all, on a liquid-crystal sidesurface of the transparent substrate SUB1, a background layer SIOconsisting of a single layer or laminated films made of SiO ₂ or SiN isformed. This background layer SIO is formed for preventing ionicimpurities contained in the transparent substrate SUB1 from givingadverse effects to a thin film transistor TFT which will be explainedlater.

[0042] Then, on a surface of this background layer SIO, a semiconductorlayer AS made of a polysilicon layer, for example, is formed. Thissemiconductor layer AS is, for example, made of material formed bypolycrystallizing an amorphous Si film which is formed by a plasma CVDapparatus using an excimer laser.

[0043] This semiconductor layer AS consists of a strip-like portionformed adjacent to the gate signal lines GL which will be explainedlater and a rectangular portion which is integrally formed with thestrip-like portion and occupies an approximately half (an upper-sidehalf in the drawing) of the pixel region.

[0044] The semiconductor layer AS of the strip-like portion is formed asa semi conductor layer of the thin film transistor TFT which will beexplained later and the semiconductor layer AS of the rectangularportion is formed as one electrode out of a pair of electrodes of thecapacity elements Cadd which will be explained later.

[0045] Then, on the surface of the transparent substrate SUB1 on whichthe semiconductor layer AS is formed, a first insulation film GI whichis made of, for example, SiO₂ or SiN and also covers the semiconductorlayer AS is formed.

[0046] This first insulation film GI functions as a gate insulation filmof the thin film transistor TFT and also functions as one of interlayerinsulation films between the gate signal lines GL and the drain signallines DL which will be explained later and one of dielectric films ofthe capacity element Cadd which wil be explained later.

[0047] Then, on the surface of the first insulation film GI, the gatesignal lines GL which are extended in the x direction and are arrangedin parallel to the y direction are formed. These gate signal lines GLdefine the rectangular pixel region together with the drain signal linesDL which will be explained later.

[0048] Here, the gate signal lines GL may be made of any conductive filmhaving the heat resistance and, for example, Al, Cr, Ta, TiW and thelike can be selected as material of the conductive film. In thisembodiment, the gate signal lines GL are made of TiW.

[0049] These gate signal lines GL have respective portions thereofextended into the inside of the pixel region and these portions aresuperposed on the strip-like semiconductor layer As such that theportion intersect the semiconductor layer As. An extension portion GL ofthe gate signal line GL is formed as a gate electrode GT of the thinfilm transistor TFT.

[0050] Here, after forming the gate signal lines GL, ion implantation ofimpurities is performed through the first insulation film GI so as tomake the region of the semiconductor layer AS except for a portion rightbelow the gate electrode GT conductive whereby the source region and thedrain region of the thin film transistor TFT can be formed and, at thesame time, one electrode out of a pair of electrodes of theabove-mentioned capacity element Cadd is formed.

[0051] Further, on the upper surface of the first insulation film GI atthe center of the pixel region, a holding capacity electrode wiring CLis formed such that the wiring CL is extended in the x direction in thedrawing. This holding capacity electrode wiring CL is integrally formedwith a holding capacity electrode CT extending to the upper side regionof the pixel region in the drawing. This holding capacity electrodewiring CL (holding capacity electrode CT) is formed as the same layer asthe gate signal lines GL and is made of the same material as the gatesignal lines GL.

[0052] On the upper surface of the first insulation film GI, a secondinsulation film IN is formed such that the film IN also covers theabove-mentioned gate signal lines GL and the holding capacity electrodewiring CL (holding capacity electrode CT). The second insulation film INis, for example, made of SiO₂ or SiN.

[0053] Further, on the upper surface of the second insulation film IN, ametal film 10 which is made of aluminum (Al) is formed such that themetal film 10 occupies approximately a half region (an upper-side regionin the drawing) of the pixel region.

[0054] This metal film 10 is connected to the semiconductor layer ASthrough contact hole CH₁ formed in the second insulation film IN and thefirst insulation film GI at the portion adjacent to the thin filmtransistor TFT.

[0055] The semiconductor layer AS which is connected with the metal film10 forms a portion which corresponds to a source region of the thin filmtransistor TFT. On the other hand, the drain region of the thin filmtransistor TFT is a region of the semiconductor layer AS opposite to thegate electrode GT while sandwiching a portion which is superposed withthe gate electrode GT and is connected with the drain signal lines DLwhich will be explained later through contact hole CH

[0056] Further, the metal film 10 is approximately extended to thecenter portion of the pixel such that the metal film 10 is superposed onthe holding capacity electrode CT.

[0057] That is, this metal film 10 constitutes a reflector which forms areflection-type pixel region and also constitutes the other electrode ofthe capacity element Cadd.

[0058] The capacity element Cadd constitutes a two-staged capacityelement in which a first capacity element which uses the holdingcapacity electrode CT as one electrode, the rectangular semiconductorlayer AS as the other electrode and the first insulation film GI as thedielectric film, and a second capacity element which uses the holdingcapacity electrode CT as one electrode, the metal film 10 as the otherelectrode and the second insulation film IN as a dielectric film areconnected in parallel between the source region and the holding capacityelectrode CT of the thin film transistor TFT (see FIG. 1).

[0059] Further, on the upper surface of the second insulation layer IN,the drain signal lines DL which are extended in the y direction and arearranged in parallel to the x direction are formed. These drain signallines DL define the pixel region together with the gate signal lines GL.

[0060] The drain signal lines DL are made of, for example, aluminum,aluminum which uses TiW as a background layer thereof or aluminum whichuses MoSi as a background layer thereof. When aluminum directly comesinto contact with the polysilicon layer, it may give rise to the poorconductance at a process temperature of not less than 400° C., forexample, and hence, it is effective to provide the background layer.

[0061] These drain signal lines DL have portions thereof connected withthe drain region of the thin film transistor TFT (the side of the thinfilm transistor TFT which is connected to the drain signal lines DL iscalled drain region in this specification) through the contact hole CH₂formed in the second insulation film IN and the first insulation filmGI.

[0062] Then, a third insulation film PSV is formed on the upper surfaceof the second insulation film IN such that the film PSV also covers thedrain signal lines DL and the metal film 10. The third insulation filmPSV is made of, for example, SiO₂ or SiN. However, the third insulationfilm PSV may be formed by coating an organic film or the like. When thethird insulation film PSV is formed by coating the organic film or thelike, the surface can be made flattened so that it becomes possible tomake the orientation of the liquid crystal have the favorable state.

[0063] A pixel electrode PIX made of ITO (Indium-Tin-Oxide) film, forexample is formed on the upper surface of the third insulation film PSV.

[0064] In this case, when the third insulation film PSV is formed of theorganic film, the occurrence of pin holes in the film can be largelysuppressed and hence, an advantageous effect that damages to the metalfilm 10 at the time of performing a patterning to form the pixelelectrode PIX of the ITO film can be prevented is obtained.

[0065] This pixel electrode PIX is connected with the metal film 10through the contact hole CH₃ formed in the third insulation film PSV ata portion adjacent to the thin film transistor TFT.

[0066] Due to such a constitution, the pixel electrode PIX is connectedwith the source region of the thin film transistor TFT through the metalfilm 10 and when the thin film transistor TFT is turned on, the videosignals from the drain signal lines are supplied to the pixel electrodePIX through the thin film transistor TFT.

[0067] Here, on the surface of the metal film 10 at the connectingportion with the pixel electrode PIX, an interposed layer 11 isselectively formed.

[0068] When aluminum (Al) or the like, for example, is used as materialof the metal film 10, the contact between the metal film 10 and the ITOfilm which constitutes the pixel electrode PIX is not favorable.Accordingly, to improve such a contact, metal such as molybdenum silicon(MoSi), titanium tungsten (TiW) or the like is inserted as theinterposed layer 11.

[0069] In this case, although it is desirable to form the interposedlayer 11 on the whole region of the metal film 10 in view of thefabrication steps, the interposed layer 11 is selectively formed in afixed range centering around the connecting portion thereof with thepixel electrode PIX in this embodiment.

[0070] It is because that since the metal film 10 is made to function asthe reflector, assume a case that the interposed layer 11 is formed onthe whole region of the metal film 10, the light reflectance is usuallydecreased due to the interposed layer 11.

[0071] Based on the above, it becomes possible to select the materialhaving the large reflectance as the metal film 10 and to make the metalfilm 10 obtain the reliable connection with the pixel electrode PIX.

[0072] Further, in this embodiment, a conducive member made of the samematerial as the interposed layer 11 is formed such that the conductivemember is superposed on the drain signal lines DL. However, it isneedless to say that the interposed layer 11 is not always necessary.

[0073] Here, the pixel electrode PIX is provided for generating anelectric field between the pixel electrode PIX and a transparent counterelectrode which is formed on a liquid-crystal side surface of othertransparent substrate (not shown in the drawing) common to respectivepixel regions which is arranged in an opposed manner to the transparentsubstrate SUB1 on which the pixel electrode PIX is formed through theliquid crystal and the optical transmissivity of the liquid crystal iscontrolled by this electric field.

[0074] In the liquid crystal display device having such a constitution,the metal film 10 which functions as the reflector is constituted suchthat it does not directly come into contact with the liquid crystal andthe third insulation film PSV and the pixel electrode PIX made ofmaterial which is hardly oxidized are interposed between the metal film10 and the liquid crystal.

[0075] Accordingly, the liquid crystal display device adopts theconstitution which hardly generates the cell action which may begenerated when the liquid crystal is interposed between the metal film10 and the other metal, and hence, an advantageous effect that thedeterioration of the liquid crystal derived from the cell action can beprevented can be obtained.

[0076] <Fabrication method>

[0077] An example of the fabrication method of the above-mentionedliquid crystal display device is explained in conjunction with FIG. 4 toFIG. 6.

[0078] Step 1 (FIG. 4(a))

[0079] The transparent substrate SUB1 having the background layer S10formed on a main surface thereof is prepared. The polysilicon layer isformed on the whole region of the surface of the background layer S10and the semiconductor layer AS is formed into a given pattern using aselective etching method based on a photolithography technique. In thiscase, the polysilicon layer is a so-called intrinsic semiconductor layerwhich is not doped with impurities.

[0080] Step 2. (FIG. 4(b)) The first insulation film GI made of, forexample, SiO₂ is formed on the whole area of the upper surface of thetransparent substrate SUB1 such that the first insulation film GI alsocovers the semiconductor layer AS.

[0081] Step 3. (FIG. 4(c))

[0082] For example, the TiW layer is formed on the whole area of theupper surface of the transparent substrate SUB1 and is formed into agiven pattern using a selective etching method based on aphotolithography technique thus forming the gate signal lines GL and theholding capacity electrode wiring GL (holding capacity electrode CL).

[0083] Then, the semiconductor layer AS which forms a layer below thefirst insulation film GI is doped with impurities, for example, byimplanting ions into the surface of the first insulation film GI onwhich such gate signal lines GL and the like are formed.

[0084] In the semiconductor layer AS, a portion thereof on which thegate electrode GT is formed constitutes a region which is not doped withimpurities since the gate electrode GT works as a mask, while otherregions are doped with impurities.

[0085] That is, in the semiconductor layer AS, a channel region of thethin film transistor TFT is formed of the portion on which the gateelectrode GT is formed and the source region and the drain region areformed at both sides of the channel region. Further, on the otherregion, one electrode of the holding capacity element Cadd which isconnected to the source region of the thin film transistor TFT isformed.

[0086] Step 4. (FIG. 5(d))

[0087] The second insulation film IN which is made of SiO₂, for example,is formed on the whole area of the upper surface of the transparentsubstrate SUB1 such that the second insulation film IN also covers theholding capacity electrode CT and the like. Thereafter, the contact holeCH₁ which penetrates the second insulation film IN and the firstinsulation film GI which forms a layer below the second insulation filmIN is formed using a selective etching method based on aphotolithography technique.

[0088] Step 5. (FIG. 5(e))

[0089] On the whole area of the upper surface of the transparentsubstrate SUB1, for example, aluminum (Al) which uses TiW as thebackground layer is formed, and is formed into a given pattern using aselective etching method based on a photolithography technique so as toform the drain signal lines DL and the metal film 10.

[0090] Step 6. (FIG. 5(f))

[0091] A metal layer made of molybdenum silicon (MoSi), for example, isformed on the whole area of the upper surface of the transparentsubstrate SUB1 and the interposed layer 11 is selectively formed using aselective etching based on a photolithography technique.

[0092] Step 7. (FIG. 6(g))

[0093] The third insulation film PSV made of resin material , forexample, is formed on the whole area of the upper surface of thetransparent substrate SUB1. Thereafter, the contact hole CH₃ whichpenetrates the third insulation film PSV is formed by a selectiveetching method based on a photolithography technique and a portion ofthe interposed layer 11 is exposed from the contact hole CH₃.

[0094] Step 8. (FIG. 6(h))

[0095] The ITO film is formed on the whole area of the upper surface ofthe transparent substrate SUB1. Thereafter, the ITO film is formed intoa given pattern using a selective etching method based on aphotolithography technique so as to form the pixel electrode PIX.

[0096] This pixel electrode PIX is connected with the interposed layer11 through the contact hole CH₃.

[0097] In the fabrication method of liquid crystal display device havingsuch a constitution, the metal film 10 is arranged to be used as oneelectrode of the holding capacity element Cadd as well as the reflector.

[0098] Accordingly, it is no more necessary to form a metal film used asa reflector and a metal film used as one electrode of the holdingcapacity element Cadd in separate steps respectively as in the case ofthe conventional method and hence, an advantageous effect that theman-hours can be reduced is obtained.

[0099] Embodiment 2.

[0100]FIG. 7 is a constitutional view showing another embodiment of theliquid crystal display device according to the present invention,wherein FIG. 7(a) is a plan view corresponding to FIG. 2 and FIG. 7(b)is a cross-sectional view taken along a line b-b of FIG. 7(a).

[0101] In FIG. 7, a constitution which differs from the constitutionshown in FIG. 2 is that the metal film 10 which also functions as thereflector is formed such that the metal film 10 is slightly extended tothe transmission-type pixel region so that the metal film 10 is mountedastride a stepped portion which is apparently formed on the surface ofthe second insulation film IN by the electrodes (AS, CT) whichconstitute the holding capacity element Cadd.

[0102] The liquid crystal display device formed in this manner isadvantageous when the priority is given to the image of a reflectiondisplay. Further, it also brings about an advantageous effect that thedeterioration of display due to the poor orientation of the liquidcrystal at the stepped portion becomes more difficult to recognize withnaked eyes in the case that the stepped portion is formed of a lightreflection region than in the case that the stepped portion is formed ofa light transmission region.

[0103] Embodiment 3

[0104]FIG. 8 is a constitutional view showing another embodiment of theliquid crystal display device according to the present invention,wherein FIG. 8(a) is a plan view corresponding to FIG. 2 and FIG. 8(b)is a cross-sectional view taken along a line b-b of FIG. 8(a).

[0105] In FIG. 7, a constitution which differs compared with theconstitution shown in FIG. 1 which is the cross-sectional view of FIG. 2is that the gate signal lines GL and the holding capacity electrode CTare formed of material having high light reflectance such as aluminum,silver or the like, for example so as to make the holding capacityelectrode CT function as the reflector.

[0106] In this case, since the metal film 10 which is made to perform afunction as the reflector in FIG. 1 has only the function as a relaylayer for enabling the connection between the semiconductor layer AS andthe pixel electrode PIX so that the metal film 10 is not extended to thecenter portion of the pixel region and is merely formed in the peripheryof the contact hole CH₁.

[0107] Different from the cases of the above-mentioned respectiveembodiments, the holding capacity element Cadd does not have amultiple-stage constitution and adopts a single stage constitution wherethe first insulation film GI is formed as the diel ectric film, oneelectrode is formed as the semiconductor layer AS, and the otherelectrode is formed as the holding capacity electrode CT.

[0108] Further, in this embodiment, the metal film 10 has an area smallenough to prevent the large intrusion into the inside of the pixelregion, so that the interposed layer 11 which enhances the connectionbetween the metal film 10 and the pixel electrode PIX is formed on thewhole area of the metal film 10 and is superposed on the drain signallines DL with the same pattern.

[0109] Accordingly, respective material layers formed in two layers canbe formed by adopting a selective etching method based on aphotolithography technique once so that the increase of fabricationman-hours can be obviated.

[0110] As can be clearly understood from the above explanation,according to the liquid crystal display device of the present invention,since the reflector can be simultaneously formed with one electrode ofthe capacity element, the fabrication steps can be decreased.

[0111] Further, since the liquid crystal display device is constitutedsuch that the connection between the reflector and the pixel electrodeis performed through the interposed layer which is selectively provided,material having the large reflectance can be selected as the reflectorand at the same time the reliability of the connection between thereflector and the pixel electrode can be enhanced.

[0112] Still further, since the liquid crystal display device isconstituted such that the reflector is formed as a layer disposed belowthe insulation film which is covered with the pixel electrode, itbecomes possible to provide the constitution which hardly generates thecell action between the reflector and other metal so that thedeterioration of the liquid crystal derived from the cell action can besuppressed.

What is claimed is
 1. A liquid crystal display device beingcharacterized in that a thin film transistor which is driven by scanningsignals from a gate signal line, a pixel electrode to which videosignals from a drain signal line are supplied through the thin filmtransistor, and a capacity element which is formed between the pixelelectrode and a holding capacity electrode are provided to each pixelregion at a liquid-crystal side of one of respective substrates whichare arranged in an opposed manner while sandwiching a liquid crystaltherebetween, the capacity element is formed such that a semiconductorlayer forming the same layer as a semiconductor layer of the thin filmtransistor, a first insulation film forming the same layer as a gateinsulation film of the thin film transistor, the holding capacityelectrode, a second insulation film and a metal layer are sequentiallylaminated from a substrate side, and the semiconductor layers and themetal layer are connected to each other, and the metal layer is formedas a reflector which occupies a portion of the pixel region.
 2. A liquidcrystal display device being characterized in that a thin filmtransistor which is driven by scanning signals from a gate signal line,a pixel electrode to which video signals from a drain signal line aresupplied through the thin film transistor, and a capacity element whichis formed between the pixel electrode and a holding capacity electrodeare provided to each pixel region at a liquid-crystal side of one ofrespective substrates which are arranged in an opposed manner whilesandwiching a liquid crystal therebetween, the capacity element isformed such that a semiconductor layer forming the same layer as asemiconductor layer of the thin film transistor, a first insulation filmforming the same layer as a gate insulation film of the thin filmtransistor, the holding capacity electrode, a second insulation film anda metal layer are sequentially laminated from a substrate side, and thesemiconductor layers and the metal layer are connected to each other,and the metal layer is formed as a reflector which occupies a portion ofthe pixel region and, at the same time, is connected to the pixelelectrode which is formed above a third insulation film formed in thepixel region such that the third insulation film covers the metal layer.3. A liquid crystal display device according to claim 2, wherein themetal layer is connected with the pixel electrode through a contact holeformed in the third insulation film, and the connection between themetal layer and the pixel electrode is performed through a conductivelayer which is selectively formed on the metal layer.
 4. A liquidcrystal display device according to any one of claim 1 and claim 2,wherein the pixel region is defined by a region which is surrounded by aplurality of gate signal lines which are extended in one direction andare arranged in the direction which intersects the one direction and aplurality of drain signal lines which intersect the gate signal linesand are arranged parallel to each other, and the holding capacityelectrode is formed as the same layer as the gate signal lines.
 5. Afabrication method of a liquid crystal display device in which acapacity element and a reflector are formed on a portion in the insideof a pixel region at a liquid crystal side of one substrate out ofrespective substrates which are arranged in an opposed manner whilesandwiching a liquid crystal therebetween, the fabrication methodcomprising steps of: a step for forming a semiconductor layer on the onesubstrate, a step for forming a first insulation film which also coversthe semiconductor layer, a step for forming a holding capacity electrodeon the first insulation film such that the holding capacity electrode issuperposed on at least a portion of the semiconductor layer, a step forforming a second insulation film such that the second insulation filmalso covers the holding capacity electrode, and a step for forming ametal layer on the second insulation film such that the metal layer isconnected to the semiconductor layer while being superposed on at leastthe holding capacity electrode, wherein the metal layer is formed as areflector.
 6. A fabrication method of the liquid crystal display deviceaccording to claim 5, wherein a thin film transistor is formed in theinside of the pixel region at the liquid crystal side of one substrateand the semiconductor layer is formed as the same layer as asemiconductor layer which constitutes the thin film transistor.
 7. Aliquid crystal display device being characterized in that a thin filmtransistor which is driven by scanning signals from a gate signal line,a pixel electrode to which video signals from a drain signal line aresupplied through the thin film transistor, and a capacity element whichis formed between the pixel electrode and a holding capacity electrodeare provided to each pixel region at a liquid-crystal side of one ofrespective substrates which are arranged in an opposed manner whilesandwiching a liquid crystal therebetween, the capacity element isformed such that a semiconductor layer forming the same layer as asemiconductor layer of the thin film transistor, a first insulation filmforming the same layer as a gate insulation film of the thin filmtransistor, and the holding capacity electrode are sequentiallylaminated from a substrate side, and the holding capacity electrode isformed as a reflector which occupies a portion of the pixel region.
 8. Aliquid crystal display device characterized in that a light reflectiontype region and a light transmission type region are providedrespectively to each pixel region at a liquid crystal side of onesubstrate out of respective substrates which are arranged in an opposedmanner through a liquid crystal, said each pixel region includes a thinfilm transistor driven by scanning signals from a gate signal line and apixel electrode to which video signals from a drain signal line aresupplied through the thin film transistor, and the connection betweenthe pixel electrode and the thin film transistor is performed in theinside of the light reflection type region.